CN105144407A - Composition for producing sealing film for solar cells and method for producing sealing film for solar cells using same - Google Patents

Abstract

Provided are a composition for producing a sealing film for solar cells and a method for producing a sealing film for solar cells. In the production of a sealing film for solar cells comprising two types of resins, when the composition for production contains an organic peroxide, it is also Film formation can be performed efficiently and favorably. A composition for producing a sealing film for a solar cell, characterized in that it is a composition for producing a sealing film for a solar cell comprising an ethylene-vinyl acetate copolymer, polyethylene, and an organic peroxide, and the JIS of the aforementioned polyethylene ? The MFR specified in K6922-1 is more than 30 g/10 minutes and 100 g/10 minutes or less, and the vinyl acetate content in the ethylene-vinyl acetate copolymer is 17 to 27% by mass.

Description

Composition for producing sealing film for solar cell and method for producing sealing film for solar cell using same

technical field

The present invention relates to a composition for producing a solar cell sealing film used for sealing a solar cell element of a solar cell, and a method for producing a solar cell sealing film using the composition.

Background technique

In recent years, solar cells that directly convert sunlight into electrical energy have been widely used from the perspectives of efficient use of resources and prevention of environmental pollution, and development has been advanced from the perspectives of durability and power generation efficiency.

A solar cell is generally produced as follows: As shown in FIG. The back-side sealing film 13B and the back-side protective member (rear cover) 12 are sequentially stacked, degassed under reduced pressure, and then the light-receiving side sealing film 13A and the back-side sealing film 13B are cross-linked and cured to bond together. to make.

Conventionally, as sealing films used in solar cells, ethylene-polar monomer copolymers such as ethylene-vinyl acetate copolymer (hereinafter also referred to as EVA) and ethylene-ethyl acrylate copolymer (EEA) have been used. film. Since it is cheap and has high transparency, it is especially preferable to use an EVA film.

In recent years, various sealing films have been developed in order to further improve the sealing properties, water vapor permeation resistance, and the like of solar cell sealing films. For example, Patent Document 1 discloses that it contains at least one resin selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, and ethylene-aliphatic unsaturated carboxylic acid ester copolymer, A sealing resin sheet (sealing film) of a mixed resin formed with a thermoplastic resin (such as polyethylene) other than this resin.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2010-59277

Contents of the invention

The problem to be solved by the invention

Therefore, as a method of crosslinking the resin contained in the sealing film for solar cells, there are: a method of crosslinking a sealing film containing an organic peroxide by heating; A method of cross-linking by beam irradiation. However, as in Patent Document 1, when two types of resins are used, temperature control becomes difficult due to exothermic heat caused by shearing when kneading the composition in the process of producing a sealing film, so that the two types of resins are mixed together. When an organic peroxide is mixed, the organic peroxide may react during kneading, and the crosslinking reaction may advance unintentionally. Therefore, when using two kinds of resins as the resin of the sealing film, the current situation is that the sealing film must be produced without compounding the organic peroxide, and it must be crosslinked by electron beam irradiation using an expensive device (see Patent Document 1, Examples 1 and 2). In order to solve this problem, it is conceivable to knead the two kinds of resins in advance, and then add additives such as organic peroxides to further knead the two kinds of resins in the range where the temperature can be adjusted. However, in this method, since the kneading process becomes 2 stage, so not only the production efficiency is reduced, but also the occurrence of foreign matter caused by the length of the process becomes a problem.

Therefore, an object of the present invention is to provide a composition for producing a sealing film for solar cells and a method for producing a sealing film for solar cells. In the production of a sealing film for solar cells comprising two kinds of resins, the composition for production contains organic Even in the case of an oxide, film formation can be efficiently and favorably performed.

solutions to problems

The above objects are achieved by a composition for producing a sealing film for a solar cell, which is characterized in that it contains an ethylene-vinyl acetate copolymer, polyethylene, and an organic peroxide A composition for producing a sealing film for a solar cell,

The MFR specified in JIS K6922-1 of the polyethylene is more than 30 g/10 minutes and 100 g/10 minutes or less, and the vinyl acetate content in the ethylene-vinyl acetate copolymer is 17 to 27% by mass.

Before molding the resin composition containing the organic peroxide into a sheet shape, it is necessary to knead the resin and each additive at a temperature that does not cause a crosslinking reaction and does not generate a molten residue of the resin. In the present invention, by using the above-mentioned specific ethylene-vinyl acetate copolymer and polyethylene, film formation can be favorably performed without causing a crosslinking reaction or melting residue of the resin during kneading. That is, if the MFR of polyethylene is within the above range, the heat generation during kneading is suppressed, so that the reaction of the organic peroxide can be prevented, and the melting residue of polyethylene can also be reduced. Furthermore, if the vinyl acetate content of EVA is the above-mentioned range, the sealing film can be efficiently mass-produced without causing adhesion or peeling to a molding machine.

The preferable aspect of the composition for manufacturing the sealing film for solar cells of this invention is as follows.

(1) The compounding mass ratio (EVA:PE) of the said ethylene-vinyl acetate copolymer and polyethylene is 8:2-3:7.

(2) The melting points of the ethylene-vinyl acetate copolymer and polyethylene measured by DSC are each 110° C. or lower.

(3) The aforementioned polyethylene is LDPE having a Mw/Mn of 4 or more.

(4) For calendering.

Moreover, the said object is attained by the manufacturing method of the sealing film for solar cells which comprises the process of kneading the kneaded material obtained by kneading the said composition for manufacturing sealing films for solar cells, and shaping|molding into a sheet shape.

The preferable aspect of the manufacturing method of the sealing film for solar cells of this invention is as follows.

(1) Before the kneading, the ethylene-vinyl acetate copolymer, the polyethylene, and the organic peroxide are premixed at a temperature lower than the kneading temperature.

(2) The temperature of the aforementioned premixing is 40-60°C.

(3) The foregoing molding is performed by calender molding.

Furthermore, the present invention provides a solar cell sealing film produced by the above production method, and a solar cell obtained by sealing a power generating element with the solar cell sealing film.

The effect of the invention

According to the composition for producing a solar cell sealing film of the present invention and the method for producing a solar cell sealing film using the same, the solar cell sealing film containing an organic peroxide can be melted without a crosslinking reaction at the production stage. Good film formation remained. Therefore, a heat-crosslinkable solar cell sealing film with high sealing properties can be produced with high quality and high efficiency.

Description of drawings

FIG. 1 is a schematic cross-sectional view of a general solar cell.

Detailed ways

Hereinafter, the present invention will be described in detail. As described above, the composition for producing a solar cell sealing film of the present invention contains ethylene-vinyl acetate copolymer (hereinafter also referred to as "EVA") and polyethylene (hereinafter also referred to as "PE"), and the vinyl acetate of EVA The ester content is 17 to 27 mass %, and the MFR of polyethylene is more than 30 g/10 minutes and 100 g/10 minutes or less.

The compounding mass ratio (EVA:PE) of an ethylene-vinyl acetate copolymer and polyethylene is preferably 8:2 to 3:7, more preferably 6:4 to 3:7. If it is this range, the composition which does not generate|occur|produce the molten residue of resin is hard to be obtained, and the adhesive performance as a sealing film can be ensured at a high level.

In this invention, content of the vinyl acetate in an ethylene-vinyl acetate copolymer is 17-27 mass %, Preferably it is 20-26 mass %. If it is this range, film formation can be performed favorably without causing the composition to stick to a molding machine or the like when molding into a sheet shape. In particular, when molding by calender molding, if the vinyl acetate content is less than 17% by mass, the composition will peel off from the calender rolls, and if it exceeds 27% by mass, the composition will stick to the calender rolls, making continuous production difficult. In the present invention, the vinyl acetate content of EVA is a value measured according to the method described in JIS K6924.

The melt flow rate of the ethylene-vinyl acetate copolymer is preferably 3 to 25 g/10 minutes, particularly preferably 4 to 20 g/10 minutes. If it is this range, fluidity suitable for film formation can be ensured, and a sealing film can be manufactured more efficiently. In the present invention, the value of the melt flow rate (MFR) of EVA is measured based on JIS K7210 under the conditions of 190° C. and a load of 21.18 N.

The polyethylene used in the present invention is a polymer mainly composed of ethylene, as specified in JIS, and includes: a homopolymer of ethylene, ethylene and 5 mol% or less of α-olefins having 3 or more carbon atoms (for example, 1-butanol) ethylene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc.), and ethylene and non-olefin monomers with only 1 mol% or less of carbon, oxygen and hydrogen atoms in the functional group Copolymer (JIS K6922-1:1997). PE is generally classified according to its density, and examples thereof include high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE).

LDPE generally has a long-chain branch obtained by polymerizing ethylene under a high pressure of 100 to 350 MPa in the presence of a free radical generator such as an organic peroxide, so its density (based on JISK7112. The same below) is generally It is 0.910 g/cm ³ or more and less than 0.930 g/cm ³ . LLDPE is generally obtained by copolymerizing ethylene and α-olefins in the presence of transition metal catalysts such as Ziegler catalysts, Philips catalysts, and metallocene catalysts, so its density is generally 0.910 to 0.940 g/cm ^3. Preferably 0.910 to 0.930 g/cm ³ . HDPE is generally polyethylene with a density of 0.942 to 0.970 g/cm ³ . The polyethylene used in the present invention is preferably LDPE (low density polyethylene) having Mw/Mn of 4 or more. If it is LDPE with such a wide molecular weight distribution, temperature dependence of viscosity becomes small, and temperature control during kneading becomes easy. The weight average molecular weight Mw of polyethylene is preferably 30,000 to 250,000, and the number average molecular weight Mn is preferably 2,000 to 25,000.

In the present invention, Mw and Mn are values calculated in terms of standard polystyrene using an dissolution profile measured by gel permeation chromatography.

In the present invention, the MFR specified in JIS K6922-1 of polyethylene is more than 30 g/10 minutes and 100 g/10 minutes or less, preferably 50 to 90 g/10 minutes. If it is 30 g/10 minutes or less, melt residues will be generated, and there will be parts where EVA and PE cannot be sufficiently mixed, so that the adhesiveness and appearance of the obtained sealing film will decrease. If it exceeds 100 g/10 minutes, the fluidity will increase, and film formation will not be performed satisfactorily.

The DSC-based melting points of polyethylene and EVA are each preferably 110° C. or lower. If it is 110° C. or less, a film-forming device controlled by water temperature can be used, so the thickness can be controlled with high precision, and the sealing film can be manufactured at low cost. The melting point in the present invention refers to a value measured in accordance with JIS K7121 using DSC.

The organic peroxide is contained in the composition for manufacturing the sealing film for solar cells before kneading of this invention. As the organic peroxide, any organic peroxide can be used as long as it decomposes at a temperature of 100° C. or higher to generate radicals. Organic peroxides are generally selected in consideration of film-forming temperature, composition adjustment conditions, curing temperature, heat resistance of an adherend, and storage stability. Particularly preferred are organic peroxides having a half-life of 10 hours and a decomposition temperature of 70° C. or higher.

Examples of the organic peroxide include benzoyl peroxide curing agents, tert-hexyl peroxypivalate, tert-butyl peroxypivalate from the viewpoint of resin processing temperature and storage stability. Esters, 3,5,5-trimethylhexanoyl peroxide, di-n-octanoyl peroxide, lauroyl peroxide, stearyl peroxide, 1,1,3,3-tetramethylbutyl peroxide- 2-ethylhexanoate, peroxysuccinic acid, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis( 2-Ethylhexanoylperoxy)hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, tert-hexylperoxy-2-ethylhexanoate, 4-methylhexanoate benzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, m-toluoyl + benzoyl peroxide, benzoyl peroxide, 1,1-bis(tert-butyl peroxide) -2-Methylcyclohexanoate, 1,1-bis(tert-hexylperoxy)-3,3,5-trimethylcyclohexanoate, 1,1-bis(tert-hexylperoxy)cyclohexanoic acid Esters, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 1,1-bis( tert-butylperoxy)-3,3,5-trimethylcyclohexane, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane, 1,1-bis(tert-butyl peroxy)cyclododecane, tert-hexyl peroxyisopropyl monocarbonate, tert-butyl peroxymaleate, tert-butyl peroxy-3,3,5-trimethylhexane, tert-butyl peroxy lauryl oxide, 2,5-dimethyl-2,5-bis(methylbenzoylperoxy)hexane, tert-butylperoxyisopropyl monocarbonate, tert-butylperoxy-2-ethyl Hexyl monocarbonate, tert-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, etc.

As the benzoyl peroxide curing agent, any benzoyl peroxide curing agent can be used as long as it decomposes at a temperature above 70°C to generate free radicals. The benzoyl oxide-based curing agent can be appropriately selected in consideration of preparation conditions, film-forming temperature, curing (sticking) temperature, heat resistance of the adherend, and storage stability. Examples of benzoyl peroxide-based curing agents that can be used include: benzoyl peroxide, 2,5-dimethylhexyl-2,5-diperoxybenzoate, p-chlorobenzoyl peroxide Formyl, m-toluoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, etc. The benzoyl peroxide curing agent may be used alone or in combination of two or more.

Among the above-mentioned organic peroxides, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane or tert-butylperoxy-2-ethylhexyl monocarbonate are preferred, tert-butyl peroxy-2-ethylhexyl monocarbonate.

Content of an organic peroxide is 0.1-5 mass parts normally with respect to 100 mass parts of total amounts of EVA and PE, Preferably it is 0.2-3 mass parts. When the content of the organic peroxide is small, the crosslinking rate may decrease during crosslinking and curing, and when it is too high, there is a possibility that the compatibility with the copolymer may deteriorate.

The composition for producing a solar cell sealing film of the present invention preferably further contains a crosslinking assistant. The cross-linking auxiliary agent can increase the gel rate of the solar cell sealing film, and improve its adhesiveness and durability.

The content of the crosslinking assistant is usually 0.1 to 5 parts by mass, preferably 0.1 to 3 parts by mass, particularly preferably 0.5 to 2.5 parts by mass, based on 100 parts by mass of the total amount of EVA and PE. Thereby, a sealing film having a further improved hardness after crosslinking can be obtained.

Examples of the aforementioned crosslinking aids (compounds having a radically polymerizable group as a functional group) include triallyl cyanurate, triallyl isocyanurate and other trifunctional crosslinking aids, And (meth)acrylate (for example, NK ester, etc.) monofunctional or difunctional crosslinking aids, etc. Among them, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable.

The composition for producing a solar cell sealing film of the present invention may further contain an adhesiveness improving agent. As the adhesion improving agent, a silane coupling agent can be used, for example, γ-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy) Silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethyl Oxysilane, β-(3,4-Ethoxycyclohexyl)ethyltrimethoxysilane, Vinyltrichlorosilane, γ-Mercaptopropyltrimethoxysilane, γ-Aminopropyltriethoxysilane , N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane. These silane coupling agents can be used individually or in combination of 2 or more types. Among them, γ-methacryloxypropyltrimethoxysilane is particularly preferably used.

Content of a silane coupling agent is desirably 5 mass parts or less with respect to 100 mass parts of total amounts of EVA and PE, Preferably it is 0.1-2 mass parts.

The composition for producing a sealing film for solar cells of the present invention is intended for the improvement or adjustment of various physical properties of the film (optical properties such as mechanical strength, transparency, heat resistance, light resistance, crosslinking speed, etc.), especially mechanical To improve the strength, various additives such as plasticizers, acryloyloxy-containing compounds, methacryloyloxy-containing compounds, and/or epoxy-group-containing compounds may be included as needed.

Next, the manufacturing method of the sealing film for solar cells of this invention is demonstrated in detail. As described above, the method for producing a solar cell sealing film of the present invention includes the step of molding a kneaded product obtained by kneading the composition for producing a solar cell sealing film of the present invention into a sheet shape. In particular, in the present invention, it is preferable to premix EVA, polyethylene, an organic peroxide, and other additives as necessary at a temperature lower than the kneading temperature before kneading. In this manner, premixing before kneading allows additives such as organic peroxides to permeate into the resin, and a homogeneous sealing film can be obtained after film formation.

The premix can be used in a mixer such as a commonly used mixer. The premixing temperature varies depending on the type of resin used, but is preferably 40 to 60°C. If it is less than this range, the organic peroxide and other additives may not be sufficiently permeated into EVA and PE. If it is higher than this range, the viscosity of the resin may decrease, and proper mixing may not be possible. In addition, the time for premixing is preferably 10 to 30 minutes. As a result, the organic peroxide and other additives are uniformly permeated into the resin (EVA and PE).

The above-mentioned kneading can be performed in a kneading machine such as a twin-screw extruder that is generally used. The temperature for kneading is, for example, 100 to 120°C. When kneading in a twin-screw extruder, the barrel temperature is preferably 5 to 15°C higher than the 1-hour half-life temperature of the organic peroxide contained in the composition, and the L/D ratio is preferably 15 or more.

Any method may be used for molding the kneaded product obtained by kneading into a sheet shape. For example, calender molding, extrusion molding, press molding, etc. can be used. In particular, in the case of calender molding, the composition of the present invention can be favorably formed into a film without sticking to the calender roll or peeling off from the calender roll. Therefore, the composition for producing a solar cell sealing film of the present invention can be advantageously used as a composition for calender molding. The thickness of the solar cell sealing film to be produced is not particularly limited, and is, for example, 0.05 to 2 mm.

The structure of the solar cell of the present invention is not particularly limited as long as it includes a structure in which a solar cell element is sealed with the solar cell sealing film of the present invention. For example, a structure in which the solar cell sealing film of the present invention exists between the light-receiving surface side transparent protective member and the back side protective member, and is cross-linked and integrated to seal the solar cell cell, etc. .

In the aforementioned solar cell, in order to sufficiently seal the power generating element, for example, as shown in FIG. It is laminated with the rear side protection member 12, and the sealing film may be cross-linked and cured by conventional methods such as heating and pressing.

When heating and pressing, for example, the laminated body on which each member is laminated can be placed in a vacuum laminator at a temperature of 135 to 180° C., a degassing time of 0.1 to 5 minutes, and a pressing pressure of 0.1 to 1.5 kg/cm ² . The pressing time is 5 to 15 minutes for heating and crimping. During this heat and pressurization, the resin contained in the light-receiving side sealing film 13A and the back side sealing film 13B is crosslinked, so that the light receiving side is sealed via the light receiving side sealing film 13A and the back side sealing film 13B. The side transparent protection member 11 , the rear side transparent member 12 , and the solar cell element 14 are integrated to seal the solar cell unit 14 .

It should be noted that the solar cell sealing film of the present invention can be used not only for solar cells using single crystal or polycrystalline silicon crystal system power generating elements as shown in FIG. 1 , but also for thin film silicon systems, thin film Sealing films for thin-film solar cells such as amorphous silicon-based solar cells and copper indium selenide (CIS)-based solar cells. In the above case, for example, the following structure can be enumerated: on the surface of a transparent protective member on the light-receiving side such as a glass substrate, a polyimide substrate, a fluororesin-based transparent substrate, or on a thin-film solar cell formed by chemical vapor deposition or the like. A structure in which the solar cell sealing film of the present invention and the back side protection member are laminated on the element layer and bonded and integrated; on the solar cell element formed on the surface of the back side protection member, the solar cell sealing film of the present invention is , the structure in which the transparent protective member on the light-receiving side is laminated and bonded together; or the transparent protective member on the light-receiving side, the sealing film on the light-receiving side, the thin-film solar cell element, the sealing film on the back side, and the protective member on the back side in order Laminated and bonded integrated structures, etc. In addition, in this invention, the cell for solar cells, and a thin-film solar cell element are collectively called a solar cell element.

The light-receiving surface-side transparent protective member 11 can generally be a glass substrate such as silicate glass. The thickness of the glass substrate is generally 0.1 to 10 mm, preferably 0.3 to 5 mm. A glass substrate can generally be strengthened chemically or thermally.

Plastic films such as polyethylene terephthalate (PET), polyamide, and the like can be preferably used for the rear side protection member 12 . In addition, in consideration of heat resistance and heat-and-moisture resistance, fluorinated polyethylene films, particularly fluorinated polyethylene films/Al/fluorinated polyethylene films, may be sequentially laminated.

Hereinafter, the present invention will be described in detail based on examples.

Example

Feed granular EVA and polyethylene into a mixer preheated to 40°C, add the following additives, and raise the temperature of the mixture to 50°C for 15 minutes while mixing, so that the additives are soaked in EVA and polyethylene. The thus obtained composition for producing a sealing film for solar cells was put into a twin-screw extruder, the barrel temperature was set at 129°C, the composition was kneaded, and the kneaded product was formed into a sheet by a calender molding machine. shape to obtain a solar cell sealing film (thickness: 0.5 mm). In addition, the conditions of kneading are as follows. L/D ratio: 20, screw composition: kneading disk, rotational speed: 80rpm.

The compounding quality ratio of EVA and polyethylene is shown in Table 1, and the details of each material are as follows.

・EVA1 (UltrasenUE515 manufactured by Tosoh Corporation), vinyl acetate content: 6% by mass, MFR: 25g/10min, melting point: 101°C

・EVA2 (UltrasenUE626 manufactured by Tosoh Corporation), vinyl acetate content: 15% by mass, MFR: 3g/10min, melting point: 90°C

・EVA3 (UltrasenUE633 manufactured by Tosoh Corporation), vinyl acetate content: 20% by mass, MFR: 20g/10min, melting point: 83°C

・EVA4 (UltrasenUE634 manufactured by Tosoh Corporation), vinyl acetate content: 26% by mass, MFR: 4.3g/10min, melting point: 76°C

・EVA5 (UltrasenUE720 manufactured by Tosoh Corporation), vinyl acetate content: 28% by mass, MFR: 150g/10min, melting point: 69°C

・EVA6 (UltrasenUE750 manufactured by Tosoh Corporation), vinyl acetate content: 32% by mass, MFR: 30g/10min, melting point: 66°C

· Polyethylene 1 (Petrothene 228 manufactured by Tosoh Corporation), LDPE, MFR: 1.5 g/10 minutes, melting point: 111° C., Mw: 200,000, Mn: 24,000, Mw/Mn: 8.3, density: 0.924 g/cm ³

· Polyethylene 2 (Petrothene 208 manufactured by Tosoh Corporation), LDPE, MFR: 23 g/10 minutes, melting point: 111° C., Mw: 110000, Mn: 15000, Mw/Mn: 7.3, density: 0.924 g/cm ³

· Polyethylene 3 (J3519 manufactured by Ube-Maruzen Polyethylene Co, Ltd.), LDPE, MFR: 35 g/10 minutes, melting point: 108° C., Mw: 90000, Mn: 13000, Mw/Mn: 6.9, density: 0.916 g/cm ³

· Polyethylene 4 (Petrothene 249 manufactured by Tosoh Corporation), LDPE, MFR: 70 g/10 minutes, melting point: 102° C., Mw: 35000, Mn: 5000, Mw/Mn: 7, density: 0.916 g/cm ³

· Polyethylene 5 (Petrothene 353 manufactured by Tosoh Corporation), LDPE, MFR: 145g/10min, melting point: 100°C, Mw: 15000, Mn: 2000, Mw/Mn: 7.5, density: 0.915g/ ^cm3

[additive]

- 1.3 parts by mass of organic peroxide (tert-butylperoxy-2-ethylhexyl monocarbonate: Perbutyl E manufactured by NOF Corporation, 1-hour half-life temperature: 119° C.)

· 1.5 parts by mass of a crosslinking auxiliary agent (triallyl isocyanurate: TAIC manufactured by Nippon Chemicals Co., Ltd.)

・Adhesion improving agent (γ-methacryloxypropyltrimethoxysilane: KBM503 manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by mass

＜Evaluation method＞

1. Molten residue

The presence or absence of molten residue of the resin was confirmed visually about the sealing film for solar cells obtained as above. The case where the melting residue of φ0.8 mm ² or more was less than 1 piece/300 mm ² was marked as “○”, and the case of φ 0.8 mm ² or more melting residue was 1 piece/300 mm ² or more was marked as “×”.

2. Film formation

In the above-mentioned calender molding, the case where continuous production of 1 series (8 hours) was possible was marked as "○", the case where peeling from the calender roll occurred during continuous production in 1 series was marked as "△", and the case of continuous production in 1 series was compared with The case where the calender rolls stuck was marked as "x".

Table 1 shows the evaluation results. It should be noted that the combination of polyethylene 3 or 4 and EVA 3 or 4 in Table 1 is an example, and the others are comparative examples. In the table, the unit of VA% is "mass %", the unit of MFR is "g/10min", and the unit of melting point Tm is "°C".

[Table 1]

＜Evaluation results＞

When using polyethylene 3 (MFR: 35g/10min) or polyethylene 4 (MFR: 70g/10min) in combination with EVA3 (VA%: 20% by mass) or EVA4 (VA%: 26% by mass), it was confirmed that The organic peroxide does not react during kneading, does not produce molten residue, and has good film-forming properties. On the other hand, when polyethylene 1 and polyethylene 2 having low MFR were used, molten residues were generated. When polyethylene 5 with a high MFR was used, it was confirmed that the film-forming property was lowered. In addition, when EVA 1 and 2 with low VA% were used, the composition peeled off from the calender rolls, and continuous production was not possible. Furthermore, when EVA5 and 6 with high VA% were used, sticking to the calender rolls occurred, and continuous production was not possible.

Explanation of reference signs

11 Transparent protective member on the light receiving surface side

12 rear side protection member

13A Light receiving surface side sealing film

13B rear side sealing film

14 Units for solar cells

Claims (11)

1. A composition for producing a sealing film for a solar cell, which is a composition for producing a sealing film for a solar cell comprising an ethylene-vinyl acetate copolymer, polyethylene, and an organic peroxide, The MFR specified in JISK6922-1 of the polyethylene is more than 30 g/10 minutes and 100 g/10 minutes or less, The vinyl acetate content in the ethylene-vinyl acetate copolymer is 17 to 27% by mass. 2. The composition for producing a solar cell sealing film according to claim 1, wherein the compounding mass ratio (EVA:PE) of the ethylene-vinyl acetate copolymer to polyethylene is 8:2 to 8:2. 3:7. 3 . The composition for producing a solar cell sealing film according to claim 1 or 2 , wherein the ethylene-vinyl acetate copolymer and the polyethylene have melting points measured by DSC of 110° C. or lower, respectively. 4 . 4 . The composition for producing a solar cell sealing film according to claim 1 , wherein the polyethylene is LDPE having a Mw/Mn of 4 or more. 5 . The composition for producing a solar cell sealing film according to claim 1 , which is used for calender molding. 6. A method for producing a sealing film for a solar cell, comprising the step of kneading a kneaded product obtained by kneading the composition for producing a sealing film for a solar cell according to any one of claims 1 to 5 Shaped into flakes. 7. The manufacturing method according to claim 6, characterized in that, before the mixing, the ethylene-vinyl acetate copolymer, the polyethylene and the organic peroxide are mixed at a temperature lower than the The pre-mixing is performed at the temperature of the kneading temperature. 8. The manufacturing method according to claim 7, characterized in that the temperature of the pre-mixing is 40-60°C. 9. The manufacturing method according to any one of claims 6 to 8, wherein the molding is performed by calender molding. The sealing film for solar cells manufactured by the manufacturing method in any one of Claims 6-9. A solar cell obtained by sealing a solar cell element with the solar cell sealing film according to claim 10.